Japanese Patent Application Publication No. 2013-223308 discloses a control apparatus for a synchronous motor. The disclosed control apparatus changes the number of triangular pulses of a periodical triangular carrier wave during one phase of each of three-phase sinusoidal command voltages in accordance with the rotational speed of the synchronous motor.
In particular, the disclosed control apparatus switches the number of triangular pulses of the triangular carrier wave during one phase of each of the three-phase sinusoidal command voltages to a different number at suitable timing to thereby reduce current ripples generated due to a phase difference between the triangular carrier wave and each of the three-phase sinusoidal command voltages. This current ripple reduction results in reduction of torque shock.